Table 1.

Spectroskopic properties and pKa of Sapphire mutants.

	λ (ex)	λ (em)	QY	ε	pKa
Sapphire	399	511	0.64	25000	4.9
T-Sapphire	399	511	0.6	44000	4.9
cpT-Sapphire 145-144	399	511	0.14	32000	5.6
cpT-Sapphire 174-173	399	511	0.53	44000	5.2

L(ex) is the peak of the excitation spectrum in units of nm. L (em) is the peak of the emission in units of nm. QY is the fluorescence quantum yield, which is dimensionless. E is the extinction coefficient in units of M^-1cm^-1.